Role of native point defects on the electronic properties of β-Cu2Se by DFT+U analysis

This study investigates the structural, electronic, and thermoelectric properties of Cu₂Se, focusing on the effects of point defects and Hubbard corrections. Using density functional theory (DFT) with the PBE functional and DFT + U corrections, we analyze lattice parameters and the electronic band structure. The pristine Cu₂Se shows metallic behavior under PBE, with no band gap and a lattice parameter deviating from experimental values. Hubbard corrections to Cu and Se atoms resolve these discrepancies, reproducing the experimental lattice parameter (5.76 Å) and band gap (1.3 eV). The study highlights the role of Cu d-electrons in lattice expansion and Se p-electrons in band gap formation. Point defects, such as Cu vacancies, enhance the Seebeck coefficient by reducing carrier concentration and shifting the Fermi level, offering a route to optimize thermoelectric performance. These findings demonstrate the importance of defect engineering and Hubbard parameter tuning in optimizing Cu₂Se for advanced applications.